The long-term objectives of this application are to understand the biological function of collagen VI and to investigate whether collagen VI is involved in connective tissue disorders. Collagen VI is an abundant microfibrillar component present in almost all tissues. It is composed of three different chains, [alpha1(VI)alpha2(VI)alpha3(VI)], encoded by three genes located on human chromosome 21 and 2. During the past eight years, the applicants have elucidated the protein and gene structures for the three chains of human collagen VI. They also have initiated studies concerning the assembly of collagen VI chains and the regulation of collagen VI gene expression. It is becoming increasingly clear that the alpha3(VI) gene plays a key role in controlling the expression of collagen VI. In this renewal application, they propose to continue studying the structure/function, assembly, and regulation of collagen VI with a major emphasis placed on the alpha3(VI) chain. They also propose to use transgenic mice approaches to investigate the biological role of collagen VI in vivo and the phenotypic consequences of mutations in collagen VI genes. The Specific Aims of this application are: 1) to investigate the structure/function and assembly of collagen VI in vitro using recombinant collagen chains and domains produced in an eukaryotic expression system; 2) to complete the characterization of collagen VI genes by developing microsatellite markers for the human alpha1(VI), alpha2(VI) and alpha3(VI) collagen genes and identifying cis- and trans- regulatory elements controlling the transcription and regulation of the human alpha3(VI) gene; 3) to investigate the expression patterns of the three collagen VI chains and the alternative spliced variants in the mouse; and 4) to study the biological role of collagen VI in vivo and the phenotypic consequences of mutations in the collagen VI gene by preparing and analyzing transgenic mice with inactivated or mutated alpha3(VI) collagen gene.